1. Field of the Invention
The invention relates to systems for transmitting one of a plurality of commands along a conductor and generating a plurality of output signals representative of the transmitted command.
2. Brief Description of the Prior Art
In various applications, such as in an automotive electronic systems, it is desirable to be able to select one of a plurality of command signals by, for example, activating one or more switches, at a "remote site" or "sending site" and have signals generated at a receiving site representative of the selected command. Apparatus for accomplishing transmission of selected commands to the receiving site have involved use of a plurality of conductors, one conductor for transmitting respectively, each selected command. Other systems have utilized a single wire or conductor coupled between the sending device and the receiving device. Use of a single conductor reduces the cost of the system by eliminating the costs associated with the use of several conductors. The apparatus at the sending site of the system has produced a different voltage level on the conductor corresponding to each of the possible selectable commands. Circuitry on the receiving end has been used to discriminate the various voltage levels on the transmission conductor to generate a plurality of binary output signals, which may then be utilized as inputs by digital logic circuitry which may perform various control functions as, for example, controlling an electronically controlled automotive cruise control system. However, the cost of the electronic discriminating circuitry for such systems is quite high, and may outweigh the cost in reducing the number of transmission conductors. Typically, a plurality of comparator circuits have been utilized to differentiate or detect each of the voltage levels that may appear on the single transmission conductor. For example, if four voltage levels, corresponding to four selectable commands, may be sent down the transmission conductor, four comparators are required, which are capable of generating four binary output signals, corresponding to the four commands.